/*
** $Id: gif.c,v 1.8 2004/08/03 11:01:57 panweiguo Exp $
** 
** gif.c: Low-level GIF file read/save routines.
** 
** Copyright (C) 2003 Feynman Software.
** Copyright (C) 2000, 2001 Wei Yongming
**
** Current maintainer: Wei Yongming
**
** Create date: 2000/08/29
*/

/*
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
** GNU General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software
** Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

/* Code for GIF decoding has been adapted from XPaint:                   */
/* +-------------------------------------------------------------------+ */
/* | Copyright 1990, 1991, 1993 David Koblas.                          | */
/* | Copyright 1996 Torsten Martinsen.                                 | */
/* |   Permission to use, copy, modify, and distribute this software   | */
/* |   and its documentation for any purpose and without fee is hereby | */
/* |   granted, provided that the above copyright notice appear in all | */
/* |   copies and that both that copyright notice and this permission  | */
/* |   notice appear in supporting documentation.  This software is    | */
/* |   provided "as is" without express or implied warranty.           | */
/* +-------------------------------------------------------------------+ */
/* Portions Copyright (C) 1999 Sam Lantinga */
/* Portions Copyright (C) 2000, 2001 Wei Yongming */
/* Adapted for use in SDL by Sam Lantinga -- 7/20/1998 */
/* Adapted for use in MiniGUI by Wei Yongming -- 8/30/2000 */
/* Adapted for Big Endian system by Wei Yongming -- 2001-11-13 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "common.h"
#include "gdi.h"
#include "readbmp.h"

#ifdef _GIF_FILE_SUPPORT

/*
 * GIF decoding routine
 */
#define MAXCOLORMAPSIZE         256
#define MAX_LWZ_BITS            12
#define INTERLACE               0x40
#define LOCALCOLORMAP           0x80

#define CM_RED                  0
#define CM_GREEN                1
#define CM_BLUE                 2

#define BitSet(byte, bit)              (((byte) & (bit)) == (bit))
#define ReadOK(file,buffer,len)        MGUI_RWread(file, buffer, len, 1)
#define LM_to_uint(a,b)                (((b)<<8)|(a))

struct {
    unsigned int Width;
    unsigned int Height;
    unsigned char ColorMap[3][MAXCOLORMAPSIZE];
    unsigned int BitPixel;
    unsigned int ColorResolution;
    unsigned int Background;
    unsigned int AspectRatio;
    int GrayScale;
} GifScreen;

static struct {
    int transparent;
    int delayTime;
    int inputFlag;
    int disposal;
} Gif89;

static int ReadColorMap(MG_RWops* src, int number,
                unsigned char buffer[3][MAXCOLORMAPSIZE], int *flag);
static int DoExtension(MG_RWops* src, int label);
static int GetDataBlock(MG_RWops* src, unsigned char *buf);
static int GetCode(MG_RWops* src, int code_size, int flag);
static int LWZReadByte(MG_RWops* src, int flag, int input_code_size);
static int ReadImage(MG_RWops* src, MYBITMAP* bmp, RGB* pal, int len, int height, int,
                unsigned char cmap[3][MAXCOLORMAPSIZE],
                int gray, int interlace, int ignore);

int __mg_load_gif (MG_RWops *src, MYBITMAP* bmp, RGB* pal)
{
    unsigned char buf[16];
    unsigned char c;
    unsigned char localColorMap[3][MAXCOLORMAPSIZE];
    int grayScale;
    int useGlobalColormap;
    int bitPixel;
    int imageCount = 0;
    char version[4];
    int imageNumber = 1;
    int ok = 0;

    if (!ReadOK (src, buf, 6))
        return ERR_BMP_IMAGE_TYPE;                /* not gif image*/
    if (strncmp((char *) buf, "GIF", 3) != 0)
        return ERR_BMP_IMAGE_TYPE;
    strncpy (version, (char *) buf + 3, 3);
    version [3] = '\0';

    if (strcmp(version, "87a") != 0 && strcmp(version, "89a") != 0) {
#ifdef _DEBUG
        fprintf (stderr, "__mg_load_gif: GIF version number is not 87a or 89a\n");
#endif
        return ERR_BMP_NOT_SUPPORTED;                /* image loading error*/
    }
    Gif89.transparent = -1;
    Gif89.delayTime = -1;
    Gif89.inputFlag = -1;
    Gif89.disposal = 0;

    if (!ReadOK (src, buf, 7)) {
#ifdef _DEBUG
        fprintf (stderr, "__mg_load_gif: bad screen descriptor\n");
#endif
        return ERR_BMP_LOAD;                /* image loading error*/
    }
    GifScreen.Width = LM_to_uint (buf[0], buf[1]);
    GifScreen.Height = LM_to_uint (buf[2], buf[3]);
    GifScreen.BitPixel = 2 << (buf[4] & 0x07);
    GifScreen.ColorResolution = (((buf[4] & 0x70) >> 3) + 1);
    GifScreen.Background = buf[5];
    GifScreen.AspectRatio = buf[6];

    if (BitSet(buf[4], LOCALCOLORMAP)) {        /* Global Colormap */
        if (ReadColorMap(src, GifScreen.BitPixel, GifScreen.ColorMap,
                         &GifScreen.GrayScale)) {
#ifdef _DEBUG
            fprintf (stderr, "__mg_load_gif: bad global colormap\n");
#endif
            return ERR_BMP_LOAD;                /* image loading error*/
        }
    }

    do {
        if (!ReadOK (src, &c, 1)) {
#ifdef _DEBUG
            fprintf (stderr, "__mg_load_gif: EOF on image data\n");
#endif
            goto done;
        }
        if (c == ';') {                /* GIF terminator */
            if (imageCount < imageNumber) {
#ifdef _DEBUG
                fprintf (stderr, "__mg_load_gif: no image %d of %d\n", imageNumber,imageCount);
#endif
                goto done;
            }
        }
        if (c == '!') {                /* Extension */
            if (!ReadOK (src, &c, 1)) {
#ifdef _DEBUG
                fprintf (stderr, "__mg_load_gif: EOF on extension function code\n");
#endif
                goto done;
            }
            DoExtension (src, c);
            continue;
        }
        if (c != ',') {                /* Not a valid start character */
            continue;
        }
        ++imageCount;

        if (!ReadOK (src, buf, 9)) {
#ifdef _DEBUG
            fprintf (stderr, "__mg_load_gif: bad image size\n");
#endif
            goto done;
        }
        useGlobalColormap = !BitSet (buf[8], LOCALCOLORMAP);

        bitPixel = 1 << ((buf[8] & 0x07) + 1);

        if (!useGlobalColormap) {
            if (ReadColorMap(src, bitPixel, localColorMap, &grayScale)) {
#ifdef _DEBUG
                fprintf (stderr, "__mg_load_gif: bad local colormap\n");
#endif
                goto done;
            }
            ok = ReadImage (src, bmp, pal, LM_to_uint(buf[4], buf[5]),
                              LM_to_uint(buf[6], buf[7]),
                              bitPixel, localColorMap, grayScale,
                              BitSet(buf[8], INTERLACE),
                              imageCount != imageNumber);
        } else {
            ok = ReadImage(src, bmp, pal, LM_to_uint(buf[4], buf[5]),
                              LM_to_uint(buf[6], buf[7]),
                              GifScreen.BitPixel, GifScreen.ColorMap,
                              GifScreen.GrayScale, BitSet(buf[8], INTERLACE),
                              imageCount != imageNumber);
        }
    } while (ok == 0);

    bmp->flags = MYBMP_FLOW_DOWN;
    if ( Gif89.transparent > 0 ) {
        bmp->flags |= MYBMP_TRANSPARENT;
        bmp->transparent = Gif89.transparent;
    }

    if(ok)
            return 0;                /* image load ok*/

done:
    return ERR_BMP_LOAD;                        /* image load error*/
}

static int
ReadColorMap (MG_RWops *src, int number, unsigned char buffer[3][MAXCOLORMAPSIZE],
    int *gray)
{
    int i;
    unsigned char rgb[3];
    int flag;

    flag = TRUE;

    for (i = 0; i < number; ++i) {
        if (!ReadOK(src, rgb, sizeof(rgb)))
            return 1;
        buffer[CM_RED][i] = rgb[0];
        buffer[CM_GREEN][i] = rgb[1];
        buffer[CM_BLUE][i] = rgb[2];
        flag &= (rgb[0] == rgb[1] && rgb[1] == rgb[2]);
    }

#if 0
    if (flag)
        *gray = (number == 2) ? PBM_TYPE : PGM_TYPE;
    else
        *gray = PPM_TYPE;
#else
    *gray = 0;
#endif

    return FALSE;
}

static int
DoExtension(MG_RWops *src, int label)
{
    static unsigned char buf[256];

    switch (label) {
    case 0x01:                        /* Plain Text Extension */
        break;
    case 0xff:                        /* Application Extension */
        break;
    case 0xfe:                        /* Comment Extension */
        while (GetDataBlock(src, (unsigned char *) buf) != 0);
        return FALSE;
    case 0xf9:                        /* Graphic Control Extension */
        GetDataBlock(src, (unsigned char *) buf);
        Gif89.disposal = (buf[0] >> 2) & 0x7;
        Gif89.inputFlag = (buf[0] >> 1) & 0x1;
        Gif89.delayTime = LM_to_uint(buf[1], buf[2]);
        if ((buf[0] & 0x1) != 0)
            Gif89.transparent = buf[3];

        while (GetDataBlock(src, (unsigned char *) buf) != 0);
        return FALSE;
    default:
        break;
    }

    while (GetDataBlock(src, (unsigned char *) buf) != 0);

    return FALSE;
}

static int ZeroDataBlock = FALSE;

static int
GetDataBlock(MG_RWops *src, unsigned char *buf)
{
    unsigned char count;

    if (!ReadOK(src, &count, 1))
        return -1;
    ZeroDataBlock = count == 0;

    if ((count != 0) && (!ReadOK(src, buf, count)))
        return -1;
    return count;
}

static int
GetCode(MG_RWops *src, int code_size, int flag)
{
    static unsigned char buf[280];
    static int curbit, lastbit, done, last_byte;
    int i, j, ret;
    unsigned char count;

    if (flag) {
        curbit = 0;
        lastbit = 0;
        done = FALSE;
        return 0;
    }
    if ((curbit + code_size) >= lastbit) {
        if (done) {
            if (curbit >= lastbit)
#ifdef _DEBUG
                fprintf (stderr,"__mg_load_gif: bad decode\n");
#endif
            return -1;
        }
        buf[0] = buf[last_byte - 2];
        buf[1] = buf[last_byte - 1];

        if ((count = GetDataBlock(src, &buf[2])) == 0)
            done = TRUE;

        last_byte = 2 + count;
        curbit = (curbit - lastbit) + 16;
        lastbit = (2 + count) * 8;
    }
    ret = 0;
    for (i = curbit, j = 0; j < code_size; ++i, ++j)
        ret |= ((buf[i / 8] & (1 << (i % 8))) != 0) << j;

    curbit += code_size;

    return ret;
}

static int
LWZReadByte(MG_RWops *src, int flag, int input_code_size)
{
    int code, incode;
    register int i;
    static int fresh = FALSE;
    static int code_size, set_code_size;
    static int max_code, max_code_size;
    static int firstcode, oldcode;
    static int clear_code, end_code;
    static int table[2][(1 << MAX_LWZ_BITS)];
    static int stack[(1 << (MAX_LWZ_BITS)) * 2], *sp;

    if (flag) {
        set_code_size = input_code_size;
        code_size = set_code_size + 1;
        clear_code = 1 << set_code_size;
        end_code = clear_code + 1;
        max_code_size = 2 * clear_code;
        max_code = clear_code + 2;

        GetCode(src, 0, TRUE);

        fresh = TRUE;

        for (i = 0; i < clear_code; ++i) {
            table[0][i] = 0;
            table[1][i] = i;
        }
        for (; i < (1 << MAX_LWZ_BITS); ++i)
            table[0][i] = table[1][0] = 0;

        sp = stack;

        return 0;
    } else if (fresh) {
        fresh = FALSE;
        do {
            firstcode = oldcode = GetCode(src, code_size, FALSE);
        } while (firstcode == clear_code);
        return firstcode;
    }
    if (sp > stack)
        return *--sp;

    while ((code = GetCode(src, code_size, FALSE)) >= 0) {
        if (code == clear_code) {
            for (i = 0; i < clear_code; ++i) {
                table[0][i] = 0;
                table[1][i] = i;
            }
            for (; i < (1 << MAX_LWZ_BITS); ++i)
                table[0][i] = table[1][i] = 0;
            code_size = set_code_size + 1;
            max_code_size = 2 * clear_code;
            max_code = clear_code + 2;
            sp = stack;
            firstcode = oldcode = GetCode(src, code_size, FALSE);
            return firstcode;
        } else if (code == end_code) {
            int count;
            unsigned char buf[260];

            if (ZeroDataBlock)
                return -2;

            while ((count = GetDataBlock(src, buf)) > 0);

            if (count != 0) {
                /*
                 * fprintf (stderr,"missing EOD in data stream (common occurence)");
                 */
            }
            return -2;
        }
        incode = code;

        if (code >= max_code) {
            *sp++ = firstcode;
            code = oldcode;
        }
        while (code >= clear_code) {
            *sp++ = table[1][code];
            if (code == table[0][code])
                fprintf (stderr, "__mg_load_gif: circular table entry\n");
            code = table[0][code];
        }

        *sp++ = firstcode = table[1][code];

        if ((code = max_code) < (1 << MAX_LWZ_BITS)) {
            table[0][code] = oldcode;
            table[1][code] = firstcode;
            ++max_code;
            if ((max_code >= max_code_size) &&
                (max_code_size < (1 << MAX_LWZ_BITS))) {
                max_code_size *= 2;
                ++code_size;
            }
        }
        oldcode = incode;

        if (sp > stack)
            return *--sp;
    }
    return code;
}

static int
ReadImage(MG_RWops* src, MYBITMAP* bmp, RGB* pal, int len, int height, int cmapSize,
          unsigned char cmap[3][MAXCOLORMAPSIZE],
          int gray, int interlace, int ignore)
{
    unsigned char c;
    int i, v;
    int xpos = 0, ypos = 0, pass = 0;

    /*
     *        Initialize the compression routines
     */
    if (!ReadOK(src, &c, 1)) {
        fprintf (stderr,"__mg_load_gif: EOF on image data\n");
        return 0;
    }
    if (LWZReadByte(src, TRUE, c) < 0) {
        fprintf (stderr,"__mg_load_gif: error reading image\n");
        return 0;
    }

    /*
     *        If this is an "uninteresting picture" ignore it.
     */
    if (ignore) {
        while (LWZReadByte(src, FALSE, c) >= 0);
        return 0;
    }
    /*image = ImageNewCmap(len, height, cmapSize);*/
    bmp->w = len;
    bmp->h = height;
    bmp->frames = 1;
    bmp->depth = 8;
    bmpComputePitch (8, len, &bmp->pitch, TRUE);
    bmp->bits = malloc (height * bmp->pitch);
    if(!bmp->bits)
            return 0;

    for (i = 0; i < cmapSize; i++) {
        /*ImageSetCmap(image, i, cmap[CM_RED][i],
                     cmap[CM_GREEN][i], cmap[CM_BLUE][i]);*/
        pal[i].r = cmap[CM_RED][i];
        pal[i].g = cmap[CM_GREEN][i];
        pal[i].b = cmap[CM_BLUE][i];
    }

    while ((v = LWZReadByte(src, FALSE, c)) >= 0) {
        bmp->bits[ypos * bmp->pitch + xpos] = v;

        ++xpos;
        if (xpos == len) {
            xpos = 0;
            if (interlace) {
                switch (pass) {
                case 0:
                case 1:
                    ypos += 8;
                    break;
                case 2:
                    ypos += 4;
                    break;
                case 3:
                    ypos += 2;
                    break;
                }

                if (ypos >= height) {
                    ++pass;
                    switch (pass) {
                    case 1:
                        ypos = 4;
                        break;
                    case 2:
                        ypos = 2;
                        break;
                    case 3:
                        ypos = 1;
                        break;
                    default:
                        goto fini;
                    }
                }
            } else {
                ++ypos;
            }
        }
        if (ypos >= height)
            break;
    }

fini:
    return 1;
}

BOOL __mg_check_gif (MG_RWops* fp)
{
    char buf[16];
    char version[4];

    if (!ReadOK (fp, buf, 6))
        return FALSE;               /* not gif image*/
    if (strncmp(buf, "GIF", 3) != 0)
        return FALSE;
    strncpy (version, buf + 3, 3);
    version [3] = '\0';

    if (strcmp(version, "87a") != 0 && strcmp(version, "89a") != 0) {
        return FALSE;               /* image loading error*/
    }

    return TRUE;
}

#endif /* _GIF_FILE_SUPPORT */

